Hitherto, there has been a combined air-conditioning and hot-water supply system that can provide high-temperature hot-water supply and indoor air-conditioning at the same time by utilizing a dual refrigerating cycle. As such a system, there has been proposed “a heat-pump-type hot-water supply device provided with a lower-stage-side refrigerant circuit in which a first refrigerant is made to flow, and in which a first compressor, a refrigerant distributing device, a first heat exchanger, a second heat exchanger, a first throttle device, an outdoor heat exchanger, a four-way valve, and the first compressor are connected in this order, and from the refrigerant distributing device, the four-way valve, the indoor heat exchanger, and a second throttle device are interposed in this order and connected between the second heat exchanger and the first throttle device, with a higher-stage-side refrigerant circuit in which a second refrigerant flows, and in which a second compressor, a condenser, a third throttle device, the first heat exchanger, and the second compressor are connected in this order, and with a hot-water supply path in which water for hot-water supply is made to flow, and in which the second heat exchanger and the condenser are connected in this order” (See Patent Literature 1 and Patent Literature 2, for example).
Also, there has been proposed an air-conditioning and hot-water supply system provided with an air conditioner provided with a refrigerant circuit for air conditioning in which a compressor, an outdoor heat exchanger, an expansion mechanism, and an indoor heat exchanger are connected and a unit-type hot-water supply device provided with a refrigerant circuit for hot-water supply in which the compressor, the first heat exchanger, the expansion mechanism, and a second heat exchanger are connected in series and into which a carbon dioxide refrigerant is filled, in which the first heat exchanger is connected to a hot-water circuit for hot-water supply that generates hot water from water and is configured to be capable of heat exchange between water of the hot-water circuit for hot-water supply and the carbon dioxide refrigerant, while the second heat exchanger has a heat radiating portion connected in parallel with the indoor heat exchanger of the refrigerant circuit for air conditioning and a heat absorbing portion connected to the refrigerant circuit for hot-water supply and is constituted by a cascade heat exchanger that exchanges heat between the refrigerant of the lower-state-side refrigerant circuit and the carbon dioxide refrigerant” (See Patent Literature 3, for example).